


only one life to lose

by msermesth



Category: Marvel, Marvel Cinematic Universe
Genre: Ambiguous/Open Ending, Bittersweet, M/M, Post-Avengers: Endgame (Movie), Post-Captain America: Civil War (Movie), Secret Identity, Time Travel, background Steve Rogers/Peggy Carter - Freeform, background Tony Stark/Pepper Potts - Freeform, old steve
Language: English
Status: Completed
Published: 2019-05-28
Updated: 2019-05-28
Packaged: 2020-03-20 14:36:03
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,344
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18994579
Author URL: https://archiveofourown.org/users/msermesth/pseuds/msermesth
Summary: “I’m from a future.” Nathan’s smile falters but his gaze doesn’t change. “And hopefully not the one you’ll see.”For Tony, that is all sorts of unsettling. “Why are you here?”Nathan pulls something from his pocket that could be a watch but clearly isn’t. “Because I need an assist, and you’re the smartest man I know.”





	only one life to lose

**Author's Note:**

> I hardcore headcanon that Steve created an alternative timeline when he went back to Peggy at the end of Endgame, and thus he needed some way to return to his original timeline. And, because I like angst, I assume he decided to wait until Peggy died and then needed to ask Tony right after Siberia and...well you can guess where my brain went.
> 
> Thank you to Mizzy for telling me Steve went by the name "Nathan Hale" in Captain America #451. It fit perfectly.
> 
> I guess it's not really a shippy fic, but I see everything through that lens.

It’s so quiet Tony hears the footsteps in the hallway. It’s so quiet he hears the nanobots forming a repulser around his hand and whirring, ready to fire, as he aims.

The intruder doesn’t shout ‘don’t shoot’. He doesn’t do much of anything except hold his hands up in the air.

Which may be asking a lot for the guy, given he can’t be a year younger than seventy-five.

“Who’re you?” Tony asks. “And why’re you here?” He should probably lower his arm, while he’s at it, but how’s he supposed to trust a guy that was able to get into the compound without triggering any alarms?

“For almost seventy years I’ve gone by name of Nathan Hale,” the man explains. He has a small smile, like there’s something a little funny about it. “And I need a favor.”

“Nathan….” Tony’s mind immediately goes to the history books on that, but the more he looks at the man and the lines around his eyes, he remembers another person he might know. “Peggy Carter’s husband?” The smile breaks in that moment, and yeah, maybe Tony shouldn’t have brought up the guy’s late wife. Tony drops his gauntleted hand in some form of apology and is glad Nathan takes it for the olive branch it is by lowering his arms to his sides and taking a few steps forward.

“Yes, exactly,” Nathan responds and he has to swallow around the words. “I know we’ve never met, but--”

“I’m sorry for you loss,” Tony says, a little too loud and a little quick. It’s what you’re supposed to say to a man who’s just lost his wife. “Peggy was a wonderful woman. The world owes her a large debt for her service.” She had been a larger than life figure in Tony’s life and a person his father always spoke of with reverence. “I meant to go to the funeral, I really did, but something else came up.”

Nathan nods. “I know. The timing wasn’t great, but the UN wasn’t going to reschedule a major vote just for Peggy.” He sat down on the couch by Tony’s desk. “And thank you for the flowers. They were beautiful.” The smile was back, but now it was sadder, less mischievous, so...familiar.

There was something off about the man. Tony had never met him, had _barely_  been aware of him growing up, but he could swear he’d seen those bright eyes before. Peggy’s husband had always been an enigma--almost a black hole of a person, barely perceptible. Tony remembered his mom once asking if he was going to join them for dinner; his father responded Nathan wasn’t much of people person.

Tony had a few reasons to doubt that was the case. Maybe it was just a product of Nathan’s advanced age, but he seemed perfectly comfortable sitting across the room. The second was, well, worth confirmation. “I read a file on you once. Top secret. You’re important.” Tony sat down again and held Nathan’s gaze. “You’re Nomad.”

There was a twitch in Nathan’s lip that gave Tony the impression he was only a little bit impressed. “I _was_ Nomad. That was a long time ago.”

“Not that long. I still remember nineteen-ninety-five.” Tony lets a beat pass for maximum effect. “ _Some of it_ , at least.”

Nathan chuckles, but it’s a subtle thing, more like a quick exhale that somehow softens his features. Tony swears he’s seen it a thousand times. “Wasn’t doing much of that back then. Kinda difficult when you’re eighty-eight.”

Tony stares back, eyes wide with shock. “Just how old are you?”

“I was born in nineteen-eighteen.” Simple, direct, to the point. Tony can do math, but he still wants to believe him when he talks with that sort of conviction.

Tony shakes it off. The man’s disarming, dangerously so, and Tony has had enough of that. And there is no way he’s as old as he says he is. “That wouldn’t make you eighty-eight in ninety-five.”

“No, it wouldn’t.” Nathan looks down, picks some lint off his pants. He has impeccable posture. “It’s hard to explain away those eleven years.”

“I’m a smart guy,” Tony says, and it has bite.

“Yes, you always were.”

Tony feels like he’s being patronized. “Who the hell are you?”

There’s a beat where Tony debates whether he needs the gauntlet after all. Nathan looks up from where’s he’s fidgeting with his wedding ring and looks right into his eyes. “What do you know about time travel?”

Another beat. Tony’s seen a lot during his time as an Avenger. He still hadn’t been expecting this. “Enough.” He knows the theory and the limitations. “I know it’s never been done before.”

“That’s the past though. I’m talking about time travel--not what has happened, but what’s going to happen.” Nathan’s holding his breath, possibly waiting for Tony to call him on his bullshit.

“And you’re from the future?”

“I’m from _a_ future.” Nathan’s smile falters but his gaze doesn’t change. “And hopefully not the one you’ll see.”

That is all sorts of unsettling. “Why are you here?”

Nathan pulls something from his pocket that could be a watch but clearly isn’t. “Because I need an assist, and you’re the smartest man I know.”

Tony takes it out of his hand. It could be a bomb, but he’s feeling risky. “You don’t know me at all,” he says as he studies the watch-like thing.

“It’s a Time GPS,” Nathan replies, apropos of nothing.

“And you want me to do what, exactly?”

Nathan’s watching him study the Time GPS, he has one of those gazes, the kind that sits heavy on the skin. “Send me back. I figured it would be easier if you had that to reverse-engineer the problem.”

Tony looks around the empty compound. This conversation is so fucking surreal. “And what makes you think I can do that?” He isn’t saying he can’t, but it just feels so impossible, so strange, so…not what he was expecting when he woke up this morning. And that’s saying a lot.

“Because you already did.” Nathan nods at the Time GPS. “That’s your invention, right there.”

The compound is so huge, too large for just Tony and this conversation. He can’t help but bitterly think that the entire team should be here, hearing this. Even if Vision was here...this is Avengers business, above-his-pay grade type of crazy. “Are you saying in the future I invent time travel?”

Nathan nods, but also qualifies with, “it wasn’t just you. But you played a key part, and I know you can do it again.”

“Ok, let me get this right, you’re from the future, despite the fact that you’ve been around all my life, and if SHIELD’s files on Nomad are correct, much, much longer than that.”

Nathan opens his mouth to say something, but Tony doesn't stop talking.

“And apparently the reason why you’re here, and not, you know, in the future, is because of an invention I created, right?” Tony’s having the strangest sense of deja vu right now. “Because apparently, in the future, we know each other well enough that you’d have access to my tech. Unless you stole it, of course.” Nathan’s doing that same eye-squinting thing Steve used to do when he was listening to you but was also too polite to insert anything to the conversation. That thing that used to either comfort Tony or infuriate him. “Which, if I’m going to believe you’re also the superhero who captured Arnim Zola in the 50’s, doesn’t seem likely.” And then, all at once, Tony connects the familiar cut of Nathan’s jaw to his birth year. “Steve?”

One nod of Steve’s head is all Tony gets for that amazing discovery. He has the fucking gall to look sheepish.

Tony blinks a couple of times. “But, you’re old.” Way older than the last time Tony had seen him, when they had been punching each other’s heads in.

Steve shrugs and it looks so similar and so different to the actions of the man he once knew. “Trust me when I say I feel older.”

Tony wants to ask more clarifying questions, more hows and wheres, and definitely a lot of whens, but they’ve already covered the basics. So instead he says, “That’s how you got in. FRIDAY didn’t send up any red flags because you have the same biometrics as Steve Rogers. Due to the fact that you _are_ Steve Rogers.”

This time, when Steve smiles, Tony can’t ignore the resemblance. “I didn’t think I’d be able to get in, honestly. I was sure you would have revoked my access credentials, but at least I’d have proof who I am when the alarms went off.”

“Why would I revoke your credentials?”

“Because, in my timeline, we’re not on good terms right now.”

“Yeah, same here,” Tony responds and he has the quell the reflex to look at the top drawer of his desk and the flip phone inside.

That tension just sits there for a while, quiet and exhausting; Tony’s instinct is to handwave any of that away--he has someone in front of him who needs help, and they’ve just handed him a new toy to play with. But…he can’t just ignore it, can’t just pretend he feels a little put upon to be taking this favor from Steve.

“I can do it, but I can’t guarantee that it’s going to be quick. I’ll give you a call when I’ve made some progress though,” he says because he was always going to do it, but he also wants this conversation to be over.

Steve pushes himself off the couch, gripping the armrest for support and taking longer to stand steady on his feet than Tony expects. “That’s ok. I have another favor to ask, though.”

Tony almost says _anything_ , but he knows it’s not true, so he settles on, “what is it?”

“I need the shield.”

Tony can feel himself blinking. “What?”

“I understand if you can’t.”

“I didn’t say I couldn’t--”

“It’s not for me, though,” Steve says, almost a plea.

“I’m not sure if I can.”

“Thank you.”

Tony puts his hands up in protest. “I didn’t promise anything.”

Steve smiles, just a little bit and doesn’t dignify that with a response. ”Would it be fine if I stay here?”

The idea of Steve looking over his shoulder makes Tony rather jumpy. “Yeah, I guess. But I understand if there is anywhere you’d rather be.”

“Here is fine,” Steve says and looks at a spot somewhere past Tony’s shoulder. “I’ve already said my goodbyes.”

There is no good way to respond to that, so Tony doesn’t even try. Instead he begins to move and hopes Steve is willing to just follow. “I can show you to the kitchen, if you’re hungry.”

Steve walks slow behind him and Tony has to will himself to reduce his speed. “Don’t worry about it. I remember where it is.” More silence. Tony looks back at Steve, who’s trailing his fingers across the glass wall. “Even when my strength began to go, my memory didn’t.”

Tony decides against making a joke about Steve’s age. It would just prolong the conversation. “Ok, I’ll leave you to it, then. I’ll be in the workshop, if you need me.”

“Ok,” is all Steve says. He’s studying one of the newspaper clippings that’s framed on the wall; it’s about Natasha’s congressional hearing a few years ago. The lines on his face are furrowed in concentration; there is a look in his eyes that Tony doesn’t like. It’s a look he’s seen on Steve too often and one he never learned how to handle without a joke.

Tony sighs and leaves for the workshop.

 

* * *

 

It’s three in the morning when Tony’s eyes begin to droop. It’s been twelve hours--at least--since his last coffee, so it’s understandable. Since he moved back into the compound he’s been keeping the coffee all the way in the kitchen to make it more difficult to drink. It’s the best option next to his doctor’s recommendation that he should just give it up.

The last ten hours have disappeared as Tony immersed himself in taking apart the Time GPS, far more comfortable thinking about the How of Steve’s time travel and not the Why. Which is exactly the reason he’s almost finished heating up the water for the French Press when he remembers Steve is supposed to be somewhere in the building. He decides to let the water wait and check to see where exactly Steve decided to lay his head for the night.

His first thought is Steve’s old bedroom, the one that’s been gathering dust over the last few months, and that Tony has been pointedly not looking at since he moved back in. The door’s closed, like it’s been, and Tony decides it would be weird to slip his head in and check to see if Steve’s ok. He’s about to return to the promise of coffee when he sees a sliver of light escaping from Natasha’s room down the hall.

“You know it’s weird to just hang out in someone’s room without their permission,” he says as he uses his hip to push open the door. Steve’s sitting on the bed, looking at him but also not really seeing him. His eyes are furrowed and his lips are pressed into a taut line.

“You’re right.” His eyes wander across the room.

“Did you just say I’m right?” Tony scoffs at the idea Steve waited this long to say that out loud, but Steve doesn’t notice. “You can go see her,” he adds, when it becomes clear that Steve’s too locked into a memory to notice anything else. Tony feels a tiny bit of bitterness at not being apart of Steve and Nat’s wonder twin thing.

“Yeah, I know. We’re in Cambodia right now, if I’m remembering correctly.”

“As far as I’m aware” Tony says, which means that was where Steve and his band of runaways were as of the last time he checked. Which just happened to be this morning. “Have you been up all this time?”

Steve stands up and he’s unsteady enough on his feet Tony reflexively reaches out to help him. Steve shrugs him off. “Not really much for sleep these days.” He hobbles out of the room, not looking back.” And you’re not the one to talk.”

Tony doesn’t take the bait. “You can stay in your old room. I’m really sure your younger self wouldn’t mind.”

“No, he wouldn’t,” Steve replies, and in his grizzled, aged voice, it sounds like something profound. He slips open the door to the room and Tony follows, not quite sure when he’s supposed to slip away and leave Steve alone to reminisce. “I always thought so many things would be different about this time.” He picks up a framed photograph on the dresser and turns to look at Tony. Tony’s seen it before, he can’t even remember when, but it’s of Steve--the one who’s young, the one who’s _gone_ \--standing next to an old Bucky Barnes. It must have been shot not long before Bucky died, only months after Steve has woken up. “I tried to save him, I really did,” this Steve says without ripping his eyes from the photo. “I thought I succeeded, but I didn’t know.”

Tony doesn’t know what that means.

“I just keep making the same mistakes.” Steve puts the frame back down, gently, like he’s trying to make sure it doesn’t look to different than how he left it. “I save Bucky, let him have a life where he could get to old age, and Hydra just clones him. I keep Hydra from infiltrating SHIELD, and they just worm their way in Stark Industries instead.” He finally looks at Tony. He appears older than he did this morning, his skin papery in the light and his eyes could be made of glass. “I’m sorry, Tony. I really am.”

Tony’s struck speechless. He’s too confused to know where to begin the line of questioning he needs, too overwhelmed to accept the premise of Steve’s words.

“I used to ask myself about the things I could have done differently, if only I could go back.” He sits heavy on the bed and opens the drawer to the bedside tables. He pulls out a cheap, faux leather notebook, and turns to the middle of it. “I was so proud of this one,” he says and holds up the notebook in explanation. On the page is a drawing of Tony. He’s calling the Iron Man armor, and pieces of it are flying to his body, but the helmet hasn't snapped shut yet and the hipster-joke t-shirt he’s wearing is still visible. On the paper, Tony’s face is furrowed in concentration at whatever he’s looking at. There’s so much movement in the drawing, so much happening, all at once, it captures the way Tony feels in the moment before he’s Iron Man, better than he could ever explain it. “I never showed it to anyone. Never showed any of it to anyone, really.” He flips through the notebook, and Tony sees it all upside down from where he’s standing above him. There’s Clint and Wanda and a street in New York he doesn’t recognize and Ultron and the view of the skyline from Avengers Tower, each a snapshot of a life.

“Did my dad know?” Tony asks because it’s the question he’s been pretending isn’t there somewhere on the edge of his brain.

Steve closes the notebook and places it back in the drawer. Tony tries not to look too closely at the contents of Steve’s beside table. “Yeah. He had to, he would have figured it out eventually, and I learned the hard way it’s best to tell people on your own terms and on theirs.”

“What did you tell him about the future?” _What did you tell him about me?_

“Nothing,” Steve answers. He’s looking around the room, maybe purposefully avoiding looking at Tony. “Or almost nothing.” Tony follows what he’s seeing instead and discovers there is so little to see in the room. A few photographs, yes, but nothing else besides dark blue sheets to indicate that it was Steve who lived here. “He had to know about Hydra, for example. But I never told him I knew you until you were born, and even then, I never said anything besides that you grew up to be a great man.”

“I should go,” Tony says, barely above a whisper and more to himself than Steve. He’s tired. He’s sore. He feels every minute he has spent working on solving time travel today.

“Is there a guest room I could stay in?” Steve asks. “It doesn’t feel right to sleep in here.”

“Yeah, sure.” Tony reaches out a hand to help him up and this time Steve accepts the help. “There’s the one down the hall we have in case Fury ever stays over.” It had never been used.

Steve leans into his arm for support and Tony walks him across the hall. “Thank you,” he says when Tony stops in the doorway.

“Sleep well, Steve.” Tony ducks in to check that there’s still a fresh toothbrush and a hotel-sized soaps in the bathroom.

“You, too, Tony.”

 

* * *

 

It takes a few weeks for Tony to crack the whole time travel thing. He tries to find ways to work on it when he can, whether it’s math equations on napkins while he’s at a dinner counting investors or building holographic models during international flights. Sometimes he takes out the Captain America shield and mindlessly works on that, too, because the work with his hands clears his brain enough to think about the greater theoretical questions.

The entire time Steve walks in and out of the workshop. He’s mostly quiet, except when he’s not. Then he’s all questions about the armor and Peter and what’s Tony working on at SI. He doesn’t ask about Bucky or the team or the years they spent rooting out Hydra from Tony’s own company. He does ask about Pepper, whether they’ve had a chance to talk after the accords, and encourages Tony to take her to dinner if he can.

But mostly he’s just quiet, like a ghost who’s forgotten that their soul has been left behind, who only knows how to get up and make toast in the morning and spend the rest of the day going through the motions. He exercises in the compound’s pool, even if Tony’s heart lurches in fear a little every time he sees him, even though he looks frailer everyday.

“Why now?” Tony asks as they’re eating a frozen pizza one night. “You could stay in this timeline longer, wait until we’ve invented time travel organically.”

Steve uses a napkin to wipe some sauce from corner of his mouth. “I’m not sure I have that sort of time,” he responds, matter-of-fact, with none of the heaviness of the implication in his voice.

Tony’s not sure if that’s true. The serum has certainly extended Steve’s life considerably, already. There is no reason to assume he couldn’t wait it out.

Then Steve adds, “And I made a promise to myself. If I can’t go back...then I failed myself.”

 _Steve and his promises,_ Tony thinks. He’s had enough of them to last a lifetime.

He excuses himself to the workshop, feeling more motivated to solve the problem in front of him than he’s been since the day Steve arrived.

 

* * *

 

“Tell me about the future.”

“No.”

“Come on. I need something, anything.”

“I can’t.”

“What happens? Is it bad, good? How do we fix it?”

“Stop, Tony.”

“Clearly, we fix it, because you’re here. Unless I invented time travel just to get you out of my hair, which, yeah, actually maybe happened. Is that it?”

“I told you I can’t say anything.”

“That’s bullshit, and you know it.”

Steve doesn’t respond.

 

* * *

 

Tony finishes the prototype on a cold fall morning. He left the windows open the night before, and the unseasonable warmth turned to chill in the night. Before he starts the machine he shrugs on a cardigan Steve left folded behind a chair sometime over the week and wonders if he really wants to do this.

He waits for Steve to wander into the workshop and in the meantime works on improvements to the Captain America shield. Steve eventually shows up, sometime in the early afternoon, and as he shuffles closer to Tony’s makeshift desk by the platform, Tony hopes he doesn’t fall.

He’s grown slower over the last few months. It’s strange, watching him age and coming to understand what’s going to happen.

“It’s ready,” Tony says. In a better situation it wouldn’t be the centenarian going on this untested trip. Tony’s brought up doing it himself a few times, just to make sure he did it right, but Steve shut him down every time. “Are you?”

“I just need to do a couple more things.” He looks at the shield, laying right next to Tony, and runs his fingers against the grooves in the vibranium surface. “Can you make another?” he asks.

“Maybe, with T’Challa’s blessing,” Tony replies. Steve picks it up, and Tony doesn’t need to hear the question before he pulls out the portfolio bag he’s been storing the shield in. “Who’s it for?” he asks as Steve slips it in. It’s certainly not for this Steve. 

“It’s for Captain America,” Steve says, and smiles as he closes the bag, a big, real, rare smile, one of the few Tony’s seen since Steve arrived.

He’s looking at Tony like Tony hung the fucking moon and Tony wants him to stop and wants it to continue and wants a lot of things, really. He’s distinctly aware that when Steve leaves, he’ll be back to wondering the compound alone, waiting for Peter to call or Vision to return. “You’ve said all of your goodbyes,” he says and hands Steve the time GPS to slip around his hand.

“All but one...” Steve holds out his hand, the one without any extra-proprietary time travel equipment on it, but pulls it away before Tony can even think to clasp it. He wraps his arms around Tony, instead, and pulls him close.

Maybe it’s the months it’s been since Tony’s been this close to someone or maybe it’s the way Steve’s settled into his mind like an old friend or maybe it’s the knowledge that he’ll never see Steve like this, Tony just doesn’t know, but he hugs back.

“Call him,” Steve mumbles into his neck where Tony feels wet tears. “Please, just do it.”

“I can’t,” Tony responds, like he’s begging, too, begging to not be put in this position, begging to let this be enough.

Steve pulls away. “I know.” He clasps his hands firm on Tony’s shoulders, like an imitation of a wise old man imparting some sage advice. “Do it anyway.”

“Why are you like this?” Tony asks and shakes his head. “Why are you always _fucking_ like this?” He means it to sound caustic but his heart isn’t in it.

Steve doesn’t say anything to that. Tony wonders if the younger version of the man would have a reply, a quick rejoinder, something, _anything_ to give Tony satisfaction.

But there’s none there to give, no answer, no ending that will fix it, just moments through which he’ll have to breathe. Steve picks up the portfolio case and walks up the stairs to the platform, leaning heavily on the railing with every step.

“Thank you, Tony,” Steve says. He activates the red and white suit.

Tony starts up platform. He searches himself for a good response, a good last word to get in, but finds he has nothing but, “good luck, Steve.”

Steve nods, presses a button on the Time GPS, and disappears.

Tony wraps the cardigan around him and waits, knowing Steve won’t return unless he picks up the phone.

**Author's Note:**

> I almost inserted a long aside about the ridiculousness of Time GPSes, but it just didn't fit the story. Hopefully next fic.
> 
> [tumblr post](https://msermesth.tumblr.com/post/185188678209/only-one-life-to-lose)


End file.
